Iron deficiency (plant disorder)


Iron deficiency is a plant disorder also known as "lime-induced chlorosis". It can be confused with manganese deficiency. Soil iron concentration is high, but can become unavailable for absorption if soil pH is higher than 6.5. Also, iron deficiency can develop if the soil is too waterlogged or has been overfertilised. Excess of elements such as manganese in the soil can interfere with plant iron uptake triggering iron deficiency.
Iron is needed to produce chlorophyll, hence its deficiency causes chlorosis. For example, iron is used in the active site of glutamyl-tRNA reductase, an enzyme needed for the formation of 5-Aminolevulinic acid which is a precursor of heme and chlorophyll.

Symptoms

Yellowing occur in the newly emerging leaves instead of the older leaves and usually seen in the interveinal region Fruit would be of poor quality and quantity. Iron deficient plants may overaccumulate heavy metals such as cadmium. Any plant may be affected, but raspberries and pears are particularly susceptible, as well as most acid-loving plants such as azaleas and camellias.

Treatment

Iron deficiency can be avoided by choosing appropriate soil for the growing conditions adding compost, manure, peat or similar organic matter applying Ammonium Sulphate as a Nitrogen fertilizer applying elemental Sulphur to the soil. Note: adding acid directly e.g. sulphuric/hydrochloric/citric acid is dangerous as you may mobilize metal ions in the soil that are toxic and otherwise bound. Iron can be made available immediately to the plant by the use of iron sulphate or iron chelate compounds. Two common iron chelates are Fe EDTA and Fe EDDHA. Iron sulphate and iron EDTA are only useful in soil up to PH 7.1 but they can be used as a foliar spray. Iron EDDHA is useful up to PH 9 but must be applied to the soil and in the evening to avoid photodegradation. EDTA in the soil may mobilize Lead, EDDHA does not appear to.